This invention relates to the determination of spark plug characteristics, and more particularly concerns a device which ascertains the operating temperature range of the spark plug.
Most spark plugs, as used in internal combustion engines, are comprised of an upper terminal, and a centered metal rod extending from said upper terminals to a spark gap positioned at the opposite extremity of the spark plug. The centered rod is embedded within a ceramic insulator of generally conical shape convergently tapered in the direction of the spark gap. The ceramic insulator terminates in an extremity through which the centered rod protrudes. A cylindrical metal sleeve surrounds the ceramic insulator adjacent the spark gap, said sleeve having a threaded exterior surface adapted to tightly engage appropriately positioned holes in the cylinder head of the engine. The spark gap is comprised of the lowermost extremity of the centered rod, emergent from the ceramic insulator and fashioned in a flat surface perpendicular to the rod axis, and an electrode attached to the sleeve and extending laterally to a position closely below the centered rod. The sleeve forms with the insulator a V-shaped annular trough centered upon the axis of the spark plug.
Each engine requires spark plugs having critically designed characteristics such as the width of the spark gap and the temperature range in which the spark plug is intended to operate. In the case of new spark plugs of uncertain manufacture, and in the case of used spark plugs wherein indicia specifying the characteristics of the spark plug have been obliterated, the operating temperature range of the spark plug is not readily apparent. It is also difficult to ascertain that a potential replacement spark plug of one manufacturer is equivalent in its heat range to the original spark plug, which may have been made by a different manufacurer.
It is accordingly an object of the present invention to provide means for quickly and easily ascertaining the thermal operating range of spark plugs of various manufacturer.
It is another object of this invention to provide a device useful in accordance with the foregoing object and adapted for manual hand-held operation.
It is a further object of the present invention to provide a device of the aforesaid nature of simple and rugged construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.